"veggie bombs" would be of use for zero momentum mode , veggies that spread/explode in all direction after reproduction, cause thebots tend to eat all food sources until only one big source remains. Maybe a sort of antigravity?
(tried out the planet eater with negative numbers seems to work, well however I do not test bots in 2.4 yet cause its to messy)
added:
Now I have got an idea a repulsive, force that first get greater with distanc ebefore becoming weaker.
for example.
G*m1*m2 *(r/20)^2/(r/20)^3